feat(L+M): configurable dashboard widget system + test framework

Phase L: Dashboard widget system
- Migration 046: dashboard_configs table (user/tenant/role fallback cascade)
- DashboardConfig model + dashboard_service with get/upsert per-user and tenant-default
- API router: GET/PUT /api/dashboard/config, GET/PUT /api/dashboard/tenant-default
- Frontend: 5 widget components (ProductionStats, QueueStatus, RecentRenders, CostOverview, WorkerStatus)
- DashboardGrid with API-backed config, DashboardCustomizeModal (checkbox selection, save/cancel)
- Dashboard.tsx: widget grid + analytics section (privileged users)
- Admin.tsx: restructured with new section order and Maintenance 2-col grid

Phase M: Test framework
- Backend: pytest-asyncio + pytest-cov + factory-boy in pyproject.toml
- conftest.py: excel_dir fixtures + async DB fixtures + mock storage/celery stubs
- Domain tests: billing_service, cache_service, notifications_service, imports_sanity
- Integration: test_api_health.py smoke test (requires running backend)
- Frontend: vitest + @testing-library/react + msw added to package.json
- vite.config.ts: test block (jsdom + globals + setupFiles)
- tsconfig.json: exclude src/__tests__ from main tsc (test runner handles its own types)
- MSW handlers for /api/auth/me, Billing.test.tsx, formatters.test.ts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/Admin.tsx

@@ -1,7 +1,7 @@
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
 import { useState } from 'react'
 import { toast } from 'sonner'
-import { UserPlus, Trash2, Pencil, ChevronDown, ChevronUp, ChevronRight, Settings, RefreshCw, CheckCircle2, XCircle, Clock, DollarSign, Layers, AlertTriangle, Upload, FileBox, Plus, X } from 'lucide-react'
+import { UserPlus, Trash2, Pencil, ChevronDown, ChevronUp, ChevronRight, Settings, RefreshCw, CheckCircle2, XCircle, Clock, DollarSign, Layers, AlertTriangle, Upload, FileBox, Plus, X, LayoutDashboard } from 'lucide-react'
 import { Link } from 'react-router-dom'
 import api from '../api/client'
 import TemplateEditor from '../components/admin/TemplateEditor'
@@ -17,6 +17,9 @@ import {
   listAssetLibraries, createAssetLibrary, deleteAssetLibrary, refreshAssetLibraryCatalog,
   type AssetLibrary,
 } from '../api/assetLibraries'
+import { getTenantDefaultDashboard } from '../api/dashboard'
+import type { WidgetConfig } from '../api/dashboard'
+import DashboardCustomizeModal from '../components/dashboard/DashboardCustomizeModal'
 
 export default function AdminPage() {
   const qc = useQueryClient()
@@ -158,6 +161,14 @@ export default function AdminPage() {
   const [smtpDraft, setSmtpDraft] = useState<Partial<Settings>>({})
   const smtp = { ...settings, ...smtpDraft } as Settings
 
+  const [showTenantDashboardModal, setShowTenantDashboardModal] = useState(false)
+  const { data: tenantDefaultWidgets } = useQuery<WidgetConfig[]>({
+    queryKey: ['tenant-default-dashboard'],
+    queryFn: getTenantDefaultDashboard,
+    enabled: isAdmin,
+    staleTime: 300_000,
+  })
+
   return (
     <div className="p-8 space-y-8">
       <h1 className="text-2xl font-bold text-content">Admin</h1>
@@ -886,6 +897,50 @@ export default function AdminPage() {
         </div>
       </div>
 
+      {/* ------------------------------------------------------------------ */}
+      {/* Dashboard Widget Configuration (admin only)                        */}
+      {/* ------------------------------------------------------------------ */}
+      {isAdmin && (
+        <div className="card">
+          <div className="p-4 border-b border-border-default flex items-center gap-2">
+            <LayoutDashboard size={16} className="text-content-muted" />
+            <div>
+              <h2 className="font-semibold text-content">Dashboard Widget-Konfiguration</h2>
+              <p className="text-xs text-content-muted mt-0.5">
+                Legt das Standard-Widget-Layout für alle Nutzer dieses Tenants fest. Nutzer können ihr eigenes Layout individuell anpassen.
+              </p>
+            </div>
+          </div>
+          <div className="p-4 flex items-center gap-4">
+            <div className="flex-1">
+              <p className="text-sm text-content-secondary">
+                Tenant-Standard:{' '}
+                <span className="font-medium text-content">
+                  {tenantDefaultWidgets && tenantDefaultWidgets.length > 0
+                    ? `${tenantDefaultWidgets.length} Widget${tenantDefaultWidgets.length !== 1 ? 's' : ''} konfiguriert`
+                    : 'Noch kein Standard festgelegt (Systemvorgabe aktiv)'}
+                </span>
+              </p>
+            </div>
+            <button
+              onClick={() => setShowTenantDashboardModal(true)}
+              className="btn-secondary text-sm flex items-center gap-2"
+            >
+              <LayoutDashboard size={14} />
+              Tenant-Standard-Dashboard bearbeiten
+            </button>
+          </div>
+        </div>
+      )}
+
+      {showTenantDashboardModal && (
+        <DashboardCustomizeModal
+          currentWidgets={tenantDefaultWidgets ?? []}
+          onClose={() => setShowTenantDashboardModal(false)}
+          tenantMode={true}
+        />
+      )}
+
       {/* ------------------------------------------------------------------ */}
       {/* Material Library link                                               */}
       {/* ------------------------------------------------------------------ */}

frontend/src/pages/Dashboard.tsx

@@ -1,9 +1,22 @@
 import { useAuthStore } from '../store/auth'
+import DashboardGrid from '../components/dashboard/DashboardGrid'
 import AdminDashboard from '../components/dashboard/AdminDashboard'
 import ClientDashboard from '../components/dashboard/ClientDashboard'
 
 export default function DashboardPage() {
   const user = useAuthStore((s) => s.user)
   const isPrivileged = user?.role === 'admin' || user?.role === 'project_manager'
-  return isPrivileged ? <AdminDashboard /> : <ClientDashboard />
+
+  return (
+    <div className="space-y-8">
+      {/* Configurable widget grid — visible to all roles */}
+      <div className="p-8 pb-0">
+        <h1 className="text-2xl font-bold text-content mb-6">Dashboard</h1>
+        <DashboardGrid />
+      </div>
+
+      {/* Role-based analytics section */}
+      {isPrivileged ? <AdminDashboard /> : <ClientDashboard />}
+    </div>
+  )
 }

frontend/src/pages/Notifications.tsx

@@ -143,14 +143,14 @@ export default function NotificationsPage() {
                   {cfg.label(n.details)}
                 </p>
                 <p className="text-xs text-content-muted mt-1">{formatTime(n.timestamp)}</p>
-                {n.action === 'excel.import_warnings' && n.details?.warnings && (
+                {n.action === 'excel.import_warnings' && !!n.details?.warnings && (
                   <ul className="mt-1.5 text-xs text-content-secondary list-disc list-inside space-y-0.5">
                     {(n.details.warnings as string[]).slice(0, 3).map((w, i) => (
                       <li key={i}>{w}</li>
                     ))}
                   </ul>
                 )}
-                {n.details?.error && (
+                {!!n.details?.error && (
                   <p className="mt-1.5 text-xs text-red-600 font-mono bg-red-50 rounded px-2 py-1 whitespace-pre-wrap break-all">
                     {String(n.details.error)}
                   </p>